The present invention relates to a plasma processing apparatus and, more particularly, to a plasma processing apparatus suitable for an apparatus in which an inductively coupled plasma source is used.
In the semiconductor device manufacturing field, a plasma apparatus of an inductively coupled plasma (ICP) type is also used for etching and surface processing of a specimen. As the ICP plasma processing apparatus in the past, there is known an ICP plasma processing apparatus described in JP-A-2007-158373 including a gas ring that forms a part of a vacuum processing chamber and includes a blowout port for a processing gas, a bell jar that covers an upper part of the gas ring to form the vacuum processing chamber, an antenna that is arranged in an upper part of the bell jar and supplies a radio-frequency magnetic field to the inside of the vacuum processing chamber and generates a plasma, a placing table for placing a wafer in the vacuum processing chamber, and a Faraday shield that is arranged between the antenna and the bell jar and to which a radio-frequency bias voltage is applied.
In general, in the plasma processing apparatus in which the ICP plasma source is used, it is known that a current distribution of an induction coil inevitably becomes non-uniform and plasma becomes non-uniform along the circumferential direction of the induction coil. This causes eccentricity of plasma, i.e., the center axis of the plasma diffusing on a wafer deviates from the center axis of the induction coil.
As means for solving this problem, JP-A-2011-103346 discloses a plasma processing apparatus in which a ring-like conductor substantially concentric with an induction antenna is arranged along the induction antenna. The ring-like conductor has a shape in which mutual inductance between the ring-like conductor and the induction antenna and mutual inductance between the ring-like conductor and plasma increase gradually according to the circulation in the circumferential direction of the ring-like conductor.